The present invention relates to a heterodyne laser instantaneous frequency measurement system.
In one preferred embodiment, the present invention is intended for use in an atomic vapor laser isotope separation (AVLIS) process which utilizes pulsed laser beams for photoionizing an atomic vapor. Optimum operation of an AVLIS process requires precise control of the frequency of the pulsed lasers used in the process. The isotope frequency shift and hyperfine splittings of optical transitions in heavy atoms are typically between 0.1 and 10 GHz. Hyperfine spectral features can have line widths of less than 10 MHz in atomic beams to more than one GHz in thermal sources. The efficiency of such a process is often dependent upon accurately placing the laser frequency on the center line of the hyperfine spectral features, requiring an absolute frequency error of less than 5 MHz. For 500 THz red light, this corresponds to a maximum fractional frequency error of one part in 10.sup.8.
In view of the above background, it would clearly be desirable to provide for a frequency measurement system which is capable of providing an accurate indication of the instantaneous frequency of a pulsed laser beam.